Abstract
We previously developed a crack propagation model to calculate crack paths using accumulated damage in micro-solder joints in semiconductor structures. We have now developed a method based on this crack propagation model, which we have called an accumulated damage model, to predict fatigue-crack propagation properties of solders. Generally, there is a correlation between crack propagation rates, da/dN, of solders and J-integral ranges, ΔJ. The correlation can be represented in an equation as a simple power relationship, given by da/dN=B[ΔJ]^q. We derive this simple power equation from our crack propagation model and Hutchinson-Rice-Rosengren singularity theory. The equation enabled us to estimate fatigue-crack propagation properties from cyclic stress-strain curves and fatigue strength properties. We used the method to predict fatigue-crack propagation properties for center-cracked plate specimens made of Sn-40Pb. The predictions were consistent with actual fatigue-crack propagation properties determined by experiment for center-cracked plate specimens made of Sn-40Pb, indicating that our method can be used to effectively predict solder fatigue-crack propagation properties.
